1. Field of the Invention
The present invention relates to trans-olefin compounds useful as an ingredient of liquid crystal composition, trans-olefin compounds useful as intermediate of pesticides, medical drugs, liquid crystal materials and the like, a process for producing those trans-olefin compounds, a liquid crystal composition containing the trans-olefin compound as an active ingredient, and a liquid crystal element using said liquid crystal composition.
2. Related Art Statement
With the recent progress in information society, a variety of display devices are getting an increasing importance as one of machine interfaces. Of such displays, planar displays and particularly liquid crystal displays (LCD) have rapidly been distributed because of their small thickness, lightness in weight, low driving voltage, and small consumption of electric power.
Among the liquid crystal elements represented by liquid crystal display, the matrix type liquid crystal elements large in the amount of information are classified into active matrix type and simple matrix type from the viewpoint of method of driving.
In the active matrix type, thin-film transistors or diodes made of polysilicon, amorphous silicon or the like are set as non-linear elements by every image element. However, the active matrix type is complicated in the process of production and low in product yield, so that it is inferior from the viewpoint of enlargement of area, reduction of cost and enhancement of density. Thus, at the present time, the simple matrix type is advantageous over the active matrix type so far as price and productivity are taken into account.
As the liquid crystal element of simple matrix type which is in practical use currently, those using TN type and STN type liquid crystals are predominant. The optical response of these elements utilizes orientation of the average liquid crystal molecular axis in a particular direction in an electric field, which is based on the dielectric anisotropy of liquid crystal molecules. Accordingly, the limit of optical response speed of these elements is of milli-second order, which is insufficient in the light of the increasing amount of information of the current time. Although a variety of driving methods have so far been proposed with the aim of overcoming this difficulty, none of those proposals can give an essential solution to the problem, so that enlargement of capacity and enhancement of density are difficult to realize by those proposals. Further, these liquid crystals are so restricted in the angle of visual field and in the quality of display as to present another important difficulty.
In 1980, N. A. Clark and S. T. Lagerwall [Applied Phys. Lett., 36, 899 (1980)] proposed a liquid crystal element utilizing a bistable liquid crystal with the aim of solving the above-mentioned essential problem of liquid crystal element. As such bistable liquid crystal, ferroelectric liquid crystals exhibiting a chiral-smectic C phase are predominantly used.
The ferroelectric liquid crystal element is essentially characterized in that (1) it shows two optically stable states, and the optically stable states are maintained as they are even after removal of electric field (bistability) and (2) the optically stable states can be switched in micro-second order (high-speed response property). Further, the ferroelectric liquid crystal element is characterized also in that (3) the liquid crystal molecules respond in a plane parallel to substrate and the cell has a small thickness, so that the visual field angle-dependence of display is small (wide angle of visual field). Accordingly, the ferroelectric liquid crystal element requires no use of expensive non-linear element unlike active matrix type, and is expected as a high-quality large-sized display which can achieve a high display capacity and a high display quality by a simple matrix method.
Recently, M. F. Bone (U.S. Pat. No. 5,047,757; JP-A-3-20715) has reported an address method of matrix array type liquid crystal cell (inverse mode or .tau.-Vmin mode) using a liquid crystal material so controlled that response time of the liquid crystal takes a minimum value at a particular voltage. In such address method, a liquid crystal element is driven by using the positive gradient region of the voltage-dependence of response time, on the basis of the fact that response time of liquid crystal takes a minimum value at a particular voltage. The use of such a driving method expectedly gives a non-flickering good image.
A liquid crystal material which can be used in such inverse mode must have a negative dielectric anisotropy at least over the high frequency number range of 1-40 kHz, in addition to the characteristic properties conventionally required of ferroelectric liquid crystal materials, namely a phase series necessary for obtaining a good state of orientation or, in other words, a phase series changing, when slowly cooled, from isotropic phase via cholesteric phase and smectic A phase into chiral smectic C phase, and a low viscosity and a high-speed response property.
Although a number of liquid crystal materials have so far been reported either on paper or verbally, all these techniques have had some unsolved problem. One of the problems is to develop a liquid crystal material exhibiting chiral smectic C phase in a sufficiently wide temperature range and showing a minimum response time at a particular electric field.
Many properties are required of a ferroelectric liquid crystal material used in an actual ferroelectric liquid crystal element, whatever driving method is adopted. At the present stage, any single compound cannot fulfil all of such requirements, but a ferroelectric liquid crystal composition prepared by mixing together a plurality of liquid crystal compounds or non-liquid crystal compounds must be used. Up to today, however, there has been discovered no liquid crystal material simultaneously satisfying these practical requirements.
Although some aspects of the present invention may be involved in the conceptions of U.S. Pat. No. 4,834,904 (Japanese patent Kohyo 62-502620) and U.S. Pat. No. 5,209,866 (Japanese Patent Kohyo 2-503434) if the factors in the general formulas presented therein are favorably combined, the compounds of the present invention are by no means mentioned concretely in these prior patents.